Linear Algebra: Parallel, Perpendicular, or Neither?

In summary, the line passing through the point P=(1,-1,1) with direction vector d=[2,3,-1] is parallel to the plane with equation 2x+3y-z=1. This is determined by the fact that the normal vector of the plane is parallel to the direction vector of the line, as shown by them being scalar multiples of each other or by their cross product being zero. Therefore, the line and plane are perpendicular.
  • #1
sdoyle
18
0

Homework Statement



The line l passes through the point P=(1,-1,1) and has direction vector d=[2,3,-1]. Determine whether l and P are parallel, perpendicular, or neither to 2x+3y-z=1.

Homework Equations


n.p=n.x, cross product, dot product


The Attempt at a Solution


Would you just relate the direction vector, d, to the normal vector, n[2,3,-1] ?
 
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  • #2
Yes, you would just relate the normal vector to the direction vector. How do they relate?
 
  • #3
they would be parallel because they are scalar multiples of one another (1 is the multiple) also the cross product would be zero indicating parallel vectors.
 
  • #4
That means that the NORMAL to the plane is parallel to the line. So what's the relation between the line and the plane?
 
  • #5
that they are perpendicular?
 
  • #6
Yes, they are.
 
  • #7
How would you prove that mathematically?
 
  • #8
What's to prove? The normal vector of the plane is parallel to the line. You proved that by showing they are scalar multiples or using the cross product. You're done.
 

What is a vector in linear algebra?

A vector in linear algebra is a mathematical object that represents both magnitude and direction. It can be thought of as an arrow in space, with a specific length and direction. In linear algebra, vectors are used to represent quantities such as forces, velocities, and electric fields.

How do you add vectors in linear algebra?

In order to add two vectors in linear algebra, you must first ensure that they are of the same dimension. Then, you simply add the corresponding components of the vectors together. For example, if vector A = [2, 4] and vector B = [1, 3], their sum would be [2+1, 4+3] = [3, 7]. This process is known as vector addition.

What is a scalar in linear algebra?

A scalar in linear algebra is a single number that is used to scale a vector. This means that the scalar is multiplied by each component of the vector. For example, if vector A = [2, 4] and scalar c = 3, then the scaled vector would be [2*3, 4*3] = [6, 12]. Scalars are used in linear algebra to perform operations such as stretching or shrinking vectors.

What is the dot product of two vectors in linear algebra?

The dot product of two vectors in linear algebra is a mathematical operation that results in a scalar. It is calculated by multiplying the corresponding components of the two vectors and then summing them together. For example, if vector A = [2, 4] and vector B = [1, 3], their dot product would be 2*1 + 4*3 = 14. The dot product is used to calculate the angle between two vectors and to determine if they are perpendicular.

What are some real-life applications of linear algebra vectors?

Linear algebra vectors have numerous real-life applications, especially in fields such as physics, engineering, and computer science. They are used to model and analyze physical systems, such as motion and forces, and to solve problems related to optimization and data analysis. In computer graphics, vectors are used to represent objects in 3D space and to perform transformations. They are also used in machine learning algorithms for tasks such as classification and dimensionality reduction.

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